1. Field of the Invention
This invention relates in general to contact control assemblies for use in circuit breakers and more particularly to a circuit breaker magnetic assembly having improved adjustment means for controlling the armature air gap of the magnetic assembly and to an improved contact support.
2. Summary of the Prior Art
In U.S. Pat. No. 3,943,473 and related patents, a magnet assembly for controlling the main contacts of the circuit breaker having a current limiter was disclosed. The magnetic assembly utilized an armature pivotally secured to a magnetically permeable yoke and an extended end on the armature operated the trip crossbar to open the main contacts of the breaker in response to moderate overcurrent conditions.
The armature air gap was adjusted by a screw extending through the bottom wall of the breaker to move the armature against the bias of a spring, towards or from the yoke, however when the armature was moved to adjust the air gap the distance between the armature end and the trip crossbar varied correspondingly. The result was that for circuit breakers requiring different current ratings before tripping the crossbar, varying the gap between the armature and trip crossbar in accordance with the current rating altered the travel distance and therefore time in which the bar was tripped. Thus the time interval for tripping the breaker in response to a selected fault or overcurrent varied in accordance with the breaker rating.
In addition the main contacts included a substantially stationary adjustably positioned contact that was supported by a coil spring. This led to contact bounce and arcing on reclosure of the contacts as the stationary contact reacted to the relatively large contact reclosing shock or forces.